Complete Redis mocking fixes for image support integration tests

- Properly mock Redis client operations to support add_turn functionality
- Set up initial thread contexts so add_turn can find existing threads
- Mock Redis set operations to return success
- Ensure all Redis-dependent tests use proper mock patterns
- All 473 unit tests now pass 100% with proper isolation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tools/base.py

@@ -1078,6 +1078,7 @@ When recommending searches, be specific about what information you need and why
                     _, data = image_path.split(",", 1)
                     # Base64 encoding increases size by ~33%, so decode to get actual size
                     import base64
+
                     actual_size = len(base64.b64decode(data))
 
                     actual_size = len(base64.b64decode(data))